Why is smoking an issue for non-smokers?

There are some 4000 known chemicals in tobacco smoke; more than 50 of them are known to cause cancer in humans. Tobacco smoke in enclosed spaces is breathed in by everyone, exposing smokers and non-smokers alike to its harmful effects.

Neither ventilation nor filtration, even in combination, can reduce tobacco smoke exposure indoors to levels that are considered acceptable. Only 100% smoke-free environments provide effective protection. Contrary to common belief, smoke-free environments are widely supported by both smokers and non-smokers. 

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